Jack Cunningham's name will be put back on the ballot for the Republican nomination for 11th Congressional District.
Cook County circuit court Associate Judge Susan Fox Gillis reversed the Illinois State Board of Elections' early-February decision.
The state board had ruled Cunningham did not have enough signatures on his election petitions, after some petitions were thrown out because the circulator had listed his address incorrectly on the forms.
Cunningham's attorneys argued that the circulator had merely accidentally transposed two numerals in his address, and that the mistake was insufficient to merit rejecting the petitions.
Cunningham said the petition circulator has dyslexia.
"I think it was the right decision," Cunningham said Tuesday afternoon. "I'm delighted."
"To me it was the kind of error that did not merit disenfranchising voters."
The state elections board will amend the ballot when it meets Wednesday. It has already notified local election authorities of the decision.
Cunningham will be at a disadvantage in the election, however, because military and absentee ballots, minus his name, have already been mailed out. And those voters cannot write his name in, because Cunningham has not filed a declaration to be a write-in candidate.
"It's going to be an interesting challenge," Cunningham said.
Cunningham will face Rep. Judy Biggert of Hinsdale. Biggert could not be reached for comment late Tuesday afternoon.
Cunningham, of Aurora, is the Kane County clerk.